U.S. patent application number 11/887088 was filed with the patent office on 2009-08-27 for terminal having a variable duplex capability.
Invention is credited to Mika P. Rinne, Pauli Seppinen.
Application Number | 20090213765 11/887088 |
Document ID | / |
Family ID | 37073121 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090213765 |
Kind Code |
A1 |
Rinne; Mika P. ; et
al. |
August 27, 2009 |
Terminal having a variable duplex capability
Abstract
A cellular telecommunications terminal having a full-duplex mode
of operation and a half-duplex mode of operation, including a first
cellular transmitter and a first cellular receiver operable, when
the terminal is in the full-duplex mode, to transmit and receive at
the same time and operable, when the terminal is in the half-duplex
mode, to transmit and receive at different times and not at the
same time; and a switching control for changing the mode of
operation of the terminal while operating in the full-duplex mode
from the full-duplex mode to the half-duplex mode.
Inventors: |
Rinne; Mika P.; (Espoo,
FI) ; Seppinen; Pauli; (Vantaa, FI) |
Correspondence
Address: |
HARRINGTON & SMITH, PC
4 RESEARCH DRIVE, Suite 202
SHELTON
CT
06484-6212
US
|
Family ID: |
37073121 |
Appl. No.: |
11/887088 |
Filed: |
April 7, 2005 |
PCT Filed: |
April 7, 2005 |
PCT NO: |
PCT/IB2005/001138 |
371 Date: |
January 2, 2009 |
Current U.S.
Class: |
370/278 |
Current CPC
Class: |
H04B 1/44 20130101; H04L
1/0025 20130101; H04B 1/56 20130101; H04L 1/0026 20130101; H04W
88/06 20130101 |
Class at
Publication: |
370/278 |
International
Class: |
H04B 7/005 20060101
H04B007/005 |
Claims
1. A cellular telecommunications terminal having a full-duplex mode
of operation and a half-duplex mode of operation, comprising: a
first cellular transmitter and a first cellular receiver operable,
when the terminal is in the full-duplex mode, to transmit and
receive at the same time and operable, when the terminal is in the
half-duplex mode, to transmit and receive at different times and
not at the same time; and a switching control for changing the mode
of operation of the terminal while operating in the full-duplex
mode from the full-duplex mode to the half-duplex mode
2. A terminal as claimed in claim 1, wherein the first cellular
transmitter and first cellular receiver use the same first
antenna.
3. A terminal as claimed in claim 1, wherein the switching control
is responsive to interference detected at the first cellular
receiver and a change in operational mode to half-duplex mode
occurs when the detected interference exceeds a threshold.
4. A terminal as claimed in claim 1, wherein the switching control
is responsive to the power output of the first cellular transmitter
and a change in operational mode to half-duplex mode occurs when
the power output exceeds a power threshold.
5. A terminal as claimed in claim 4, further comprising a duplexer
joining the first cellular transmitter and first cellular receiver
to the first antenna element, wherein the isolation provided by the
duplexer between the first cellular transmitter and first cellular
receiver is adequate while the power output of the first
transmitter does not exceed the power threshold and is inadequate
when the power output of the first transmitter exceeds the power
threshold
6. A terminal as claimed in claim 1, further comprising: a second
cellular transmitter and a second cellular receiver.
7. A terminal as claimed in claim 6, wherein the switching control
is responsive to interference detected using the second cellular
receiver and a change in operational mode to half-duplex mode
occurs when the detected interference exceeds a threshold.
8. A terminal as claimed in claim 6, wherein the switching control
is responsive to the power output of the second cellular
transmitter and a change in operational mode to half-duplex mode
occurs when the power output exceeds a threshold.
9. A terminal as claimed in claim 6, wherein the half duplex mode
is one of: a) transmission from a single antenna without
simultaneous reception at the single antenna; b) simultaneous
transmissions from a first antenna and a second antenna without
simultaneous reception at the first or second antenna; c)
simultaneous reception at a first antenna and a second antenna
without simultaneous transmission from the first or second
antenna.
10. A terminal as claimed in claim 6, wherein the full duplex mode
is one of: a) transmission from a single antenna with simultaneous
reception at the single antenna; b) simultaneous transmissions from
a first antenna and a second antenna with simultaneous reception at
the first or second antenna; c) simultaneous receptions at a first
antenna and a second antenna with simultaneous transmission from
the first or second antenna; d) simultaneous receptions at a first
antenna and a second antenna with simultaneous transmissions from
the first and second antennas;
11. A terminal as claimed in claim 6, comprising a switching
element joining the second cellular transmitter and second cellular
receiver to a second antenna element, and wherein the full-duplex
mode is one of: a) transmission from the first antenna element with
simultaneous reception at the first antenna element; b)
simultaneous transmissions from the first antenna element and the
second antenna element with simultaneous reception at the first
antenna element but not at the second antenna element; and c)
simultaneous reception at the first antenna element and the second
antenna element with simultaneous transmission from the first
antenna element but not from the second antenna element.
12. A terminal as claimed in claim 1 further comprising signalling
control for controlling the sending of a capability message
indicating the full-duplex-capability of the terminal.
13. A terminal as claimed in claim 1 further comprising signalling
control for controlling the sending of a capability message
indicating a reduced-duplex-capability of the terminal.
14. A terminal as claimed in claim 12, wherein the capability
message indicates the duplex capability of multiple antennas.
15. A cellular telecommunications terminal having a full-duplex
mode of operation and a half-duplex mode of operation, comprising:
a plurality of cellular transmitters and receivers; and a
controller for controlling at least one of the transmitters to
transmit a capability message indicating the duplex capability of
each of multiple antennas.
16. A terminal as claimed in claim 15, wherein the current duplex
capability of an antenna may change and wherein the controller
controls at least one of the transmitters to transmit an updated
capability message, indicating the current duplex capability of
each of multiple antennas, in response to such a change.
17. A terminal as claimed in claim 16, wherein the current duplex
capability of an antenna changes as a result of high
self-interference measurements.
18. A terminal as claimed in claim 16, wherein the duplex
capability of an antenna changes as a result of high transmission
power measurements.
19. A cellular telecommunications network element comprising: a
controller arranged to use a received capability message indicating
the duplex capability of each of multiple antennas of a terminal to
allocate resources in the network.
20. A cellular telecommunications terminal having a full-capability
mode of operation in which at least one antenna is capable of
full-duplex operation and a reduced-capability mode of operation in
which the at least one antenna is capable of half-duplex operation,
the terminal comprising: a plurality of cellular transmitters and
receivers; and a controller for controlling at least one of the
transmitters to transmit a capability message indicating the
reduced-capability mode of operation.
21. A terminal as claimed in claim 20, wherein the capability
message is sent as a result of high self-interference
measurements.
22. A terminal as claimed in claim 20, wherein the capability
message is sent as a result of high transmission power
measurements.
23. A cellular telecommunications network element comprising: a
controller arranged to use a received capability message indicating
the reduced-capability mode of operation to allocate resources in
the network.
Description
FIELD OF THE INVENTION
[0001] Embodiments of the present invention relate to a cellular
telecommunications terminal. In particular, they relate to
terminals having different duplex capabilities.
BACKGROUND TO THE INVENTION
[0002] It is known to have cellular telecommunications terminals
that operate in a half-duplex mode i.e. they do not transmit and
receive at the same time. An example of such a terminal is a GSM
mobile telephone and some GPRS mobile telephones.
[0003] It is known to have cellular telecommunications terminals
that operate in a full-duplex mode i.e. they transmit and receive
at the same time. An example of such a terminal is a high-end GPRS
mobile telephone and a WCDMA mobile telephone.
[0004] A dual mode telephone may therefore change its duplex
capability by switching from a GSM mode of operation to a WCDMA
mode of operation. The RF circuitry and antennas used for
respectively operating in the GSM mode and WCDMA mode will
typically be different and separate.
[0005] A key component of a full-duplex terminal is a duplexer
which connects the transmitter and receiver to the antenna and
prevents the symbols transmitted by the transmitter interfering
with the symbols received by the receiver. Duplexers are expensive,
consume power and have a large volume. It would therefore be
desirable to reduce the use of duplexers or to use cheaper, less
power hungry and smaller duplexers.
[0006] Currently duplexers are designed to provide enough isolation
between the receiver and transmitter when the transmitter is
operating at maximum power. If this constraint were relaxed, it may
be possible to use cheaper, less power hungry and smaller
duplexers.
[0007] There is a current trend towards the use of multiple
antennas within a terminal. These antennas each have their own
associated channels or may diversify a channel. However, the
addition of multiple antennas typically also requires the use of
multiple duplexers to isolate every receiver branch from every
transmitter branch. It would be desirable to provide for the use of
multiple antennas without the use of a duplexer at each
antenna.
BRIEF DESCRIPTION OF THE INVENTION
[0008] According to one embodiment of the invention there is
provided a cellular telecommunications terminal having a
full-duplex mode of operation and a half-duplex mode of operation,
comprising: a first cellular transmitter and a first cellular
receiver operable, when the terminal is in the full-duplex mode, to
transmit and receive at the same time and operable, when the
terminal is in the half-duplex mode, to transmit and receive at
different times and not at the same time; and a switching control
for changing the mode of operation of the terminal while operating
in the full-duplex mode from the full-duplex mode to the
half-duplex mode.
[0009] The switching control may also change the mode of operation
of the terminal while operating in the half-duplex mode from the
half-duplex mode to the full-duplex mode.
[0010] The terminal may consequently either operate at its full
capability i.e. in full-duplex mode or at a reduced capability i.e.
half-duplex mode. The switch between modes may, for example, occur
when the duplexer separating the first transmitter and the first
receiver reaches its isolation limit. This may, for example, be
detected by detecting the self-interference at the first receiver
from the first transmitter or by detecting the power of
transmission from the first transmitter.
[0011] The ability of the terminal to operate at different duplex
capabilities allows the network to allocate resources according to
those capabilities. The terminal may inform the network of its
current duplex capabilities
[0012] The network further offers any terminal, with any defined
duplex capability, resources to efficiently operate in the network.
The terminal may, but need not, be able to switch its duplex
capability, but it shall be able to uniquely signal its duplex
capability.
[0013] According to another embodiment of the invention there is
provided a cellular telecommunications terminal having a
full-duplex mode of operation and a half-duplex mode of operation,
comprising: a plurality of cellular transmitters and receivers; and
a controller for controlling at least one of the transmitters to
transmit a capability message indicating the duplex capability of
each of multiple antennas.
[0014] The terminal may have a fixed duplex capability or it may
have a variable duplex capability. If the duplex capability is
variable, then the capability message may indicate the current
capability of the terminal.
[0015] According to another embodiment of the invention there is
provided a cellular telecommunications network element comprising:
a controller arranged to use a received capability message
indicating the current duplex capability of each of multiple
antennas, of a terminal to allocate resources in the network.
[0016] According to another embodiment of the invention there is
provided a cellular telecommunications terminal having a
full-capability mode of operation in which at least one antenna is
capable of full-duplex operation and a reduced-capability mode of
operation in which the at least one antenna is capable of
half-duplex operation, the terminal comprising: a plurality of
cellular transmitters and receivers; and a controller for
controlling at least one of the transmitters to transmit a
capability message indicating the reduced-capability mode of
operation.
[0017] According to another embodiment of the invention there is
provided a cellular telecommunications network element comprising:
a controller arranged to use a received capability message
indicating the reduced-capability mode of operation to allocate
resources in the network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a better understanding of the present invention
reference will now be made by way of example only to the
accompanying drawings in which:
[0019] FIG. 1 illustrates a cellular telecommunications system 1
including a cellular telecommunications network 2 and a plurality
of cellular telecommunication terminals 10A, 10B, 10C;
[0020] FIG. 2 illustrates a full-duplex capable cellular
telecommunications terminal;
[0021] FIG. 3 illustrates a message exchange between the terminal
10 and the network 2; and
[0022] FIG. 4 schematically illustrates a full-duplex capable,
multi-antenna terminal 10'
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0023] FIG. 1 illustrates a cellular telecommunications system 1
including a cellular telecommunications network 2 and a plurality
of cellular telecommunication terminals 10A, 10B, 10C. Each cell 4
of the network is served by a base station 6 and the base stations
are controlled by core network elements 8.
[0024] One of the cellular telecommunications terminals may be
half-duplex capable. The half-duplex capable terminal comprises a
first cellular transmitter for transmitting in a first transmission
frequency band, a first cellular receiver for receiving in a first
reception frequency band, different to the first transmission
frequency band. The half-duplex terminal does not include any
duplexer.
[0025] At least one of the cellular telecommunications terminals 10
is full-duplex capable. The full-duplex capable terminal 10 is
schematically illustrated in FIG. 2. It comprises a first cellular
transmitter 21 for transmitting in a first transmission frequency
band, a first cellular receiver 31 for receiving in a first
reception frequency band, different to the first transmission
frequency band, and a duplexer 41 joining the first cellular
transmitter 21 and first cellular receiver 31 to a first antenna
51. In other embodiments, the duplexer may, instead of being placed
where the Rx path and Tx path join the antenna, it may be placed in
either the Rx path or the Tx path.
[0026] The terminal 10 has a full-duplex mode of operation in which
the first cellular transmitter 21 transmits symbols from the first
antenna 51 and the first cellular receiver 31 simultaneously
receives symbols via the first antenna 51. The isolation provided
by the duplexer 41 prevents the transmitted symbols interfering
with the received symbols i.e. prevents self-interference.
[0027] The terminal 10 has a half-duplex mode of operation in which
transmission and reception occurs at different times and not at the
same time. The first cellular transmitter 21 transmits symbols from
the first antenna 51 at first times and the first cellular receiver
31 receives symbols via the first antenna 51 at second times,
different to the first times.
[0028] The terminal 10 additionally comprises a controller 12. The
controller 12 provides a switching control 14 and signalling
control 16.
[0029] Switching control 14 changes the mode of operation of the
terminal 10. When the terminal is operating in the full-duplex
mode, the switching control 14 can change the operation mode from
the full-duplex mode to the half-duplex mode. When the terminal 10
is operating in the half-duplex mode, the switching control 14 can
change the operational mode from the half-duplex mode to the
full-duplex mode.
[0030] The trigger for the switching control 14 may be provided by
any one of a number of different means.
[0031] In one embodiment, a signal received from the network 2 via
receiver 31 functions as the trigger.
[0032] In another embodiment, the trigger is the connection of the
device 10 to another device such as a docking station with external
antennas or improved power supply etc.
[0033] In another embodiment, self-interference detection performed
at the terminal 10 functions as the trigger. The interference in
the symbols received at the first cellular receiver is detected.
The received signal strength indicator (RSSI), the received
signal-to-interference ratio (SIR), the received interference
power, the bit error rate (BER), the frame error rate (FER) etc may
be used as a measure of interference. A measure of self
interference may, for example, be obtained by measuring
interference power when the transmitter is on and measuring
interference power when the transmitter is off. The change in
operational mode to half-duplex mode is triggered when the detected
(self) interference exceeds a first predetermined interference
threshold. The change in operational mode back to full-duplex mode
is triggered when the detected (self) interference falls beneath a
second predetermined interference threshold. The first and second
thresholds may be different (bi-stability) or the same. Crossing a
threshold may involve timing constraints to avoid too frequent
change of modes.
[0034] In another embodiment, the power output of the cellular
transmitter 21 functions as the trigger. The change in operational
mode to half-duplex mode is triggered when the power output exceeds
a first predetermined power threshold. The change in operational
mode back to full-duplex mode is triggered when the power output
falls beneath a second predetermined power threshold, which is
typically the same as the first predetermined threshold but may be
different. The power threshold may be dependent upon the
characteristics of the duplexer. In one example, the predetermined
power threshold is chosen so that the isolation provided by the
duplexer 41 between the first cellular transmitter 21 and first
cellular receiver 31 is adequate while the power output of the
first transmitter 21 does not exceed the predetermined threshold
and is inadequate when the power output of the first transmitter 21
exceeds the predetermined threshold.
[0035] In a preferred embodiment, the switching control 14 is not
immediately responsive to a trigger but first exchanges messages
with the network 2 before making the change in operational mode as
illustrated in FIG. 3. In response to a trigger, the signalling
control 16 of the controller 12 controls the first transmitter 21
to send a request message 71 to the network 2. The request message
71 identifies the new operational mode and may be sent as a
capability information message.
[0036] If the first receiver 31 of the terminal 10 receives a reply
message 72 from the network 2, the switching control 14 changes 73
the operational mode of the terminal. The switch may optionally be
delayed until further confirmation of the switch is received from
the network 2.
[0037] The messages 71, 72 may be discrete messages or may be
included as Information elements in some other messages.
[0038] The network 2 changes the resource allocation 74 to take
account of the change in mode of the terminal 10. For example, if
the terminal 10 were in full-duplex mode there is no constraint
upon when the terminal 10 is expected to transmit to the network 2
and is transmitted to by the network 2. However, if the mode of the
terminal 10 is changed to half-duplex, then transmissions to the
terminal and transmissions from the terminal are constrained so
that they do not coincide. The constraint is such that enough guard
time is left between transmission and reception at the terminal 10.
Network 2 also has to reserve proper measurement intervals for
terminal 10 to measure carriers on other frequencies, carriers on
other frequency bands or carriers of other systems, so that the
measurement intervals do not coincide with terminal transmissions
to the network 2 nor transmissions by the network 2 to terminal
10.
[0039] A full-duplex capable, multi-antenna terminal 10' is
schematically illustrated in FIG. 4. It comprises the same
components as described with reference to FIG. 2 but additionally
comprises a second cellular transmitter 22, a second cellular
receiver 32 and a switch element 51 joining the second cellular
transmitter 22 and the second cellular receiver 32 to a second
antenna 52. The first and second transmitters operate on the same
carrier frequency. The first and second receivers operate on the
same carrier frequency. The carrier frequency of the transmitters
is separate from the carrier frequency of the receivers. In some
examples, the carrier frequency of the transmitters may be the same
as the carrier frequency of the receivers, if proper constraints
are respected for transmission and reception. In some examples, the
first and second transmitters may operate on separate carrier
frequencies or on carriers on separate frequency bands.
Respectively, the first and second receiver may operate on separate
carrier frequencies or on carriers on separate frequency bands.
[0040] The terminal 10' may only use one of its first and second
transmitters and operate in a single input to uplink (SI-u) mode.
The SI-u mode may be either a Single Input Single Output (SISO)
mode, if the base station has a single receiver antenna or a Single
Input Multiple Output (SIMO) mode, if the base station has more
than one receiver antenna.
[0041] The terminal 10' may use both of its first and second
transmitters and operate in a multiple input to uplink (MI-u) mode,
The MI-u mode may be either a Multiple Input Single Output (MISO)
mode, if the base station has a single receiver antenna or a
Multiple Input Multiple Output (MIMO) mode, if the base station has
more than one receiver antenna.
[0042] The terminal 10' may use one of its first and second
receivers and operate in a single output from downlink (SO-d) mode.
The SO-d mode may be either a SISO mode, if the base station has a
single transmitter antenna or a MISO mode, if the base station has
more than one transmit antennas.
[0043] The terminal 10' may use both of its first and second
receivers and operate in a multiple output from downlink (MO-d)
mode. The MO-d mode may be either a SIMO mode if the base station
has a single transmitter antenna or a MIMO mode if the base station
has more than one transmitter antenna.
[0044] The terminal 10' may operate as a single input uplink (SI-u)
terminal by using only one of the transmitters 21, 22 and as a
single output downlink (SO-u) terminal by using only one of the
receivers 31, 32. For example, if only the first transmitter 21 and
first receiver 31 are used, then the terminal 10' may operate as
either a full-duplex or half-duplex SISO terminal. If only the
second transmitter 22 and the second receiver 32 are used, then the
terminal 10' may operate as only a half-duplex SISO terminal.
[0045] The terminal 10' may operate as a multiple input single
output (MISO) terminal by using both of the transmitters 21, 22
(MI-u) and only one of the receivers 31, 32 (SO-d). If the receiver
used is the first receiver 31, then the terminal 10' may operate as
either a full-duplex or half-duplex (MISO) terminal 10'. If the
receiver used is the second receiver 32, then the terminal 10' may
operate as only a half duplex (MISO) terminal 10'.
[0046] The terminal 10' may operate as a single input multiple
output (SIMO) terminal by using one of the transmitters 21, 22
(SI-u) and both of the receivers 31, 32 (MO-d). If the transmitter
used is the first transmitter 21, then the terminal 10' may operate
as either a full-duplex or half duplex (SIMO) terminal 10'. If the
transmitter used is the second transmitter 22, then the terminal
10' may operate as only a half duplex (SIMO) terminal 10'.
[0047] The terminal 10' may operate as a multiple input multiple
output (MIMO) terminal by using both of the transmitters 21, 22
(Ml-u) and both of the receivers 31, 32 (MO-d). The terminal 10'
may operate as only a half duplex MIMO terminal. If the switch 61
were replaced by a duplexer, terminal 10' may operate as a
full-duplex MIMO terminal instead. If the duplexer 41 were
originally replaced by a switch, terminal 10' may operate as only a
half duplex terminal.
[0048] It will therefore be appreciated that the use of a switch
element 61 instead of a duplexer 41 between the second transmitter
22 and the second receiver 32, constrains some of the multi-antenna
modes of the terminal 10' to half-duplex modes, whereas if a
duplexer were used there would be an option of using either
half-duplex or full-duplex modes. However, the reduction in the
number of duplexers has significant advantages. Duplexers are
expensive, consume power and occupy a large volume. These
disadvantages become particularly problematic in multi-antenna
terminals. Consequently the terminal 10' may be cheaper, smaller
and more efficient than conventional multi-antenna terminals that
use only duplexers.
[0049] The capability of the terminal 10' namely that only
half-duplex is available for some combinations of the SI-u and MI-u
modes with the SO-d and MO-d modes needs to be communicated to the
network so that it can be taken into account in network resource
allocation.
[0050] The signalling control 16 of the controller 12 controls the
first transmitter 21 to send a message 71 to the network 2. The
message indicates duplex capability for each mode combination
(SISO, SIMO, MISO, MIMO). The message may for example, indicate for
each antenna of the terminal 10', whether an antenna is associated
with a transmitter and receiver that are full-duplex capable or a
transmitter and receiver that are not full-duplex capable. The
message may be extended to indicate whether an antenna is
associated with a transmitter only or a receiver only. The message
71 may be a discrete message or may be included as Information
elements in some other message.
[0051] The terminal 10' may switch between full-duplex mode and
half-duplex mode on a transition from using a single antenna to
using multiple antennas or on any transition between multi-antenna
configurations from SISO to SIMO, MISO or MIMO, from SIMO to SISO,
MISO or MIMO, from MISO to SISO, SIMO or MIMO or from MIMO to SISO,
SIMO or MISO.
[0052] Even when the terminal is capable of operating at
full-duplex e.g. during MIMO modes (SISO, SIMO, MISO, MIMO), the
terminal 10 may instead operate with reduced capabilities e.g.
half-duplex within its set of full capabilities. A decision to
operate with reduced capabilities may be made by the terminal 10'
or the network. If it is made by the terminal, it needs to be
communicated to the network. A convenient way of communicating is
to send a new message 71 to the network 2 that identifies the
reduced capabilities of the terminal 10' e.g. half-duplex at SISO,
half-duplex at SIMO, half-duplex at MISO or half-duplex at
MIMO.
[0053] The terminal 10' is able to switch between full-capabilities
(e.g. full-duplex mode) and reduced capabilities (e.g. half-duplex
mode). Switching control 14 changes the operational capabilities of
the terminal 10'. When the terminal 10' is operating in the
full-duplex mode, the switching control 14 can change the
operational mode from the full-duplex mode to the half-duplex mode.
When the terminal 10 is operating in the half-duplex mode, the
switching control 14 can change the operational mode from the
half-duplex mode to the full-duplex mode (if possible).
[0054] The trigger for the switching control 14 may be provided by
any one of a number of different means.
[0055] In one embodiment, a signal received from the network 2 via
the transmitter 21, 22 functions as the trigger.
[0056] In another embodiment, the trigger is the connection of the
device 10 to another device such as a docking station with external
antennas or improved power supply etc.
[0057] In another embodiment, self-interference detection performed
at the terminal 10 functions as the trigger. While one receiver 31,
32 is used to receive symbols the other receiver 32, 31 is used to
measure interference. A measure of self interference may be
obtained by measuring interference when the transmitter is on and
measuring interference when the transmitter is off. The change in
operational mode to half-duplex mode is triggered when the detected
(self) interference exceeds a first predetermined interference
threshold. The change in operational mode back to full-duplex mode
is triggered when the detected (self) interference falls beneath a
second predetermined interference threshold. The first and second
thresholds may be different (bi-stability) or the same. Crossing a
threshold may involve timing constraints to avoid too frequent
change of modes.
[0058] In another embodiment, the power output of the cellular
transmitter 21 functions as the trigger. The change in operational
mode to half-duplex mode is triggered when the power output exceeds
a first predetermined power threshold. The change in operational
mode back to full-duplex mode is triggered when the power output
falls beneath a second predetermined power threshold, which is
typically the same as the first predetermined threshold but may be
different. Crossing a threshold may involve timing constraints to
avoid too frequent change of modes. The power threshold may be
dependent upon the characteristics of the duplexer 41.
[0059] The use of the power output or self-interference as the
trigger is useful for a reduced full-duplex capability
implementation. In this implementation, the device is capable of
operating in full-duplex mode unless one of the transmit power or
self-interference exceeds their respective predetermined
thresholds. The predetermined power threshold is chosen so that the
isolation provided by the duplexer 41 between the first cellular
transmitter 21 and first cellular receiver 31 is adequate while the
power output of the first transmitter 21 does not exceed the
predetermined threshold and is inadequate when the power output of
the first transmitter 21 exceeds the predetermined threshold.
[0060] In a full-duplex implementation, the duplexer is capable of
operating across the whole power and signal-to-noise ratio range of
values.
[0061] It should be appreciated that in the foregoing, the
full-duplex and half-duplex modes of operation are different modes
of the same mobile telephone mode. That is the same FDD
communication protocol is used in the full-duplex and half-duplex
modes of operation.
[0062] Although embodiments of the present invention have been
described in the preceding paragraphs with reference to various
examples, it should be appreciated that modifications to the
examples given can be made without departing from the scope of the
invention as claimed.
* * * * *